Caddisflies, or sedges, are one of the three major orders of aquatic insects relevant to stream anglers, and yet mayflies and stoneflies receive much more attention in fly-fishing literature. The challenge with caddisflies is that they are a lot harder to identify and unless you dedicate time to understanding them, matching the hatch for caddisflies can be confusing. To keep it simple, many anglers tie on a generic elk hair caddis or Mikulak sedge to imitate caddis, but by doing this you miss an opportunity to take full advantage of the smorgasbord of caddisflies.
Life of a Caddis
Caddisflies have a complete metamorphosis, transforming from larva to pupa to adult. Most caddisflies have a one-year life cycle, but a few larger species such as the October Caddis require two years to complete their life cycle.
The larvae occupy all types of water in a river. They live in these habitats as either caseless caddis or larvae that build shelters. These shelters can be tube-shaped mobile cases, or stationary cases like those built by net-spinning caddis. When the larvae are mature, they spin cocoons inside their existing cases or build new dome-shaped shelters with small pebbles. Once inside the cocoons, the larvae take two to eight weeks to develop into pupae. Emerging from the cocoon the pupae then either ascend to the water surface to hatch, or crawl along the bottom to the shore and emerge on land. Adult caddisflies live anywhere from one to four weeks and are available as fish food during this time. After mating, the females return to the stream to lay their eggs.
In the angling community many caddisflies have two common names – one name describes the larva and the other describes the adult.
There are nearly 300 species of caddisflies in British Columbia, more than mayflies and stoneflies combined. At first glance it may seem daunting but many species within a Genus, or even a family, look and behave very similar to one another. To keep it simple, focus on the following caddis:
1. Spotted Sedge, also known as Tan Caddis or Cinnamon Caddis (Larva: Net-Spinning Caddis)
2. Green Sedge (Larva: Free-living Sedge or Green Rock Worm)
3. Grannom or Black Caddis (Larva: Grannom or Chimney-Case Caddis)
4. Black Dancer or Long Horn Caddis
5. October Caddis or Giant Orange Sedge
6. Late Summer Sedge
Spotted Sedge, also known as Tan Caddis or Cinnamon Caddis
(Larva: Net-Spinning Caddis)
The Spotted Sedge is one of the most abundant and important caddisflies to anglers, with 23 species in BC belonging to two genera Hydropsyche and Cheumatopsyche in the Hydropsychidae family. The larvae are called net-spinning caddis as they construct nets from silk. The head and three-plated thorax of a typical larva is dark brown, and the abdomen is either olive-brown, tan, olive-green or bright green. The adults are often named for the colour of their spotted wings, hence other names such as Tan or Cinnamon Caddis. As a fairly diverse group they are imitated by flies tied on hooks anywhere from size 10 to size 16.
The net-spinning larvae prefer the rocky bottom riffles and runs to spin their nets to capture food. As the larvae are abundant in streams, fish feed on them year-round, especially when the larvae disperse during behavioural drifts downstream in early mornings and late afternoons.
Spotted sedges hatch on the water from April to October in the afternoons and evenings. A couple of days after mating the females, return in the afternoon to lay their eggs. Depending on the species, the females may either crawl into the river or dive down to the bottom to deposit their eggs.
Green Sedge (Larva: Free-living Sedge or Green Rock Worm)
Green Sedges belong to Genus Rhyacophilia with 37 species in BC. The different species' larvae vary greatly in size and are imitated with flies tied on hooks from size 8 to 14. The larvae are known as free-living or caseless sedges and are also called Green Rock Worm due to the bright green colour of their abdomens. The adults have green coloured abdomens with wings that are mottled brown and gray.
The larvae inhabit riffles and are often washed downstream giving fish opportunity to intercept them. Green Sedges hatch on the water and when the females return to deposit their eggs in the afternoon, they either crawl into the river or they dive to the bottom. Green Sedges hatch from April to October, providing a steady food supply for fish.
Grannom or Black Caddis (Larva: Grannom or Chimney-Case Caddis)
This caddisfly's claim to fame is the large Mother's Day caddis hatch in the USA. Although Grannom hatches are not as intense in BC, they are still an important hatch to match. Grannoms are small and are imitated with flies tied onto size 14 to 18 hooks. The adult has a green abdomen with dark gray markings on the dorsal side, and wings that are either light gray, tan, or black. The larvae build cases from plant material that are shaped like chimneys, tapered with squared sides that are symmetrical. This case is often called a chimney-case or log-cabin case. The larvae will be peaking out with dark heads and legs that are almost black. This is in stark contrast to their abdomens that are bright green or tan. You will see these little 'log cabins' in riffles and runs with good flow, or clinging to plants in streams.
There are two species of Grannoms in BC and they hatch at two different times during the season. The first hatch of Brachycentrus occidentalis starts in May, around Mother's Day, and continues until June. The second hatch of Brachycentrus americanus occurs in the summer months of August and September. Grannoms hatch in open water and after mating, the females return to deposit their eggs by either crawling into the stream or by diving down to the bottom.
Black Dancers or Long Horn Caddis
Black Dancer caddisflies of the Genus Mystacides belong to the long horn caddisfly family Leptoceridae. This caddis has extraordinarily long antennae with black wings, and they fly erratically along the shoreline vegetation. To imitate this caddis use fly patterns tied onto size 16 and 18 hooks.
The larvae of Black Dancers build long narrow tubes using conifer needles, other organic matter, and small pebbles. Look for the larvae in slower moving water such as back eddies and shallow water closer to shore.
When ready to hatch, the pupae swim to the surface where the adult emerges in open water. This hatch takes place in the mornings from June to July. To lay their eggs, the females return in the early evening to deposit them on the surface.
Black Dancers are just one member of long horn caddisflies in BC. There are others species such as the Spotted Long Horn Caddis (Oecetis) that can be important on some rivers.
October Caddis or Giant Orange Sedge
October Caddis belongs to the Genus Dicosmoecus, with two species in BC – D. gilvipes and D. atripes. This caddisfly is large and is imitated using flies tied onto 2XL long size eight to ten hooks. The mature larvae are also easily recognized as they grow up to 40-mm long and have cases built from small stones. The larvae have white, bright yellow or tan abdomens with dark gray legs and heads. The adults have bright orange legs and abdomens, and wings that are gray with distinctive black venation.
October Caddis has a two-year life cycle as many of the streams in BC are cold, delaying development of the larvae. The larvae prefer pools and runs, and will migrate to shallower water to start the pupation process. The pupae then emerge from the water by crawling out onto land. A few weeks later the adult females return to deposit their eggs in the early evening by running across the surface, creating a V-wake. In BC October Caddis hatch from September to October.
Late Summer Sedge
This caddis belongs to the Genus Onocosmoecus. Another big caddis, it is imitated by flies tied onto size ten hooks. The larvae prefer slower moving water in rivers such as pools and runs. They look a lot like October Caddis larvae, except the cases of the mature larvae are built from plant material. The adult is very distinctive looking as the wings, legs and body is ginger to orange in colour.
Anglers not familiar with their caddisflies often confuse this caddis with the October Caddis. Mostly because it is quite common to see both flying around a stream at the same time. Late Summer Sedges hatch from August to September, just before October Caddis.
The caddisflies covered in this article highlight the most important hatches across the province. If you focus on these six you should be good to go for the vast majority of caddisfly hatches.
Six Caddisflies for BC Streams
by Danie Erasmus
First published in Mar/Apr 2019